Quote Originally Posted by browningautorifleicon View Post
You may have to inside neck ream also as the case will be thicker there now. If you've seated bullets, it's like the snake that swallowed an egg...too fat. Also you will have to reduce the load by a bit because the remaining case will be thicker and not have as much inside case space.

Why would this keep a cartridge from seating?
Hard brass has a spring back property to it. This is what makes extraction of the case easy and why "cartridge brass" (70% copper/30% zinc) is used for cartridge cases.. Upon firing, the case expands and seals the breech, (its primary function) then the case contracts slightly and releases its grip on the chamber walls.
This same spring back occurs when reforming the case. You either have to push it slightly further into the die so after springback, the case will chamber properly, or anneal the area where the new neck and shoulder will be formed to make that area soft. The annealed area will then not spring back.
All in all, a lot of effort. You have to do it for antique arms where cases are no longer made, but if new factory brass is available at a reasonable price, it makes more sense to buy.